1. Field of the Invention
The present invention relates to an industrial machine, and more particularly relates to a three-dimensional measuring instrument.
2. Description of Related Art
Conventionally, there is known a three-dimensional measuring instrument as an industrial machine having a moving mechanism that moves a probe as an object to be controlled, provided to measure a measured object, in an X-axis direction, a Y-axis direction, and a Z-axis direction perpendicular to each other; and a controlling device that controls a position of the probe by controlling a position of the moving mechanism (for example, see Related Art 1).
In such a three-dimensional measuring instrument, the moving mechanism has a portal frame as an X-axis direction moving mechanism that is provided in a vertical direction (Z-axis direction) to move the probe in the X-axis direction within a horizontal plane; a slider as a Y-axis direction moving mechanism that is provided in the Z-axis direction in a state of being movable along the Y-axis direction in a horizontal portion extending in the Y-axis direction of the portal frame to move the probe in the Y-axis direction; and a spindle as a Z-axis direction moving mechanism that is provided in the slider in a state of being movable along the Z-axis direction to support and move the probe in the Z-axis direction.
An incremental-type linear encoder is provided in each axis direction moving mechanism. A signal based on a position of each axis direction moving mechanism in each axis direction is sent from the linear encoder to the controlling device. Based on this signal, feedback control is performed to a position of the probe in each axis direction by the controlling device.    Related Art 1: Japanese Translation Publication of PCT International Application No. 2009-527747
However, in such a three-dimensional measuring instrument, since the incremental-type linear encoder is used, a position of the probe is not known immediately after power activation. In order to recognize the position of the probe in such a case, an operation is required to detect an original position of the linear encoder set in advance after the power activation of the three-dimensional measuring instrument, and it takes time to detect such a position. Consequently, it takes time to start measurement by the three-dimensional measuring instrument. This situation becomes significant when a position of the probe at the time of power activation is greatly apart from the original position of the linear encoder especially in a large-size three-dimensional measuring instrument.